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Tsirkin" , Stefano Garzarella , =?UTF-8?q?Alex=20Benn=C3=A9e?= , Akihiko Odaki , Dmitry Osipenko Subject: [PATCH v2] hw/display/virtio-gpu: cap submit_3d command buffer allocation Date: Thu, 16 Jul 2026 14:50:23 +0400 Message-ID: <20260716105023.3246364-1-marcandre.lureau@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists1p.gnu.org; Received-SPF: permerror client-ip=170.10.129.124; envelope-from=marcandre.lureau@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.01, SPF_HELO_PASS=-0.001, T_SPF_PERMERROR=0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1784199073539158500 From: Marc-Andr=C3=A9 Lureau Both virgl_cmd_submit_3d() and rutabaga_cmd_submit_3d() pass the guest-controlled cs.size directly to malloc() without bounds checking. A malicious guest can set cs.size to an arbitrarily large value, causing an OOM abort that crashes the QEMU process. Checking cs.size against the descriptor payload length (iov_size) is not sufficient: indirect descriptor tables can repeat entries aliasing the same guest-physical range, inflating iov_size() to nearly 4 GiB while referring to only a small amount of unique memory. Instead, cap cs.size at 4 MiB. With 4 KiB pages and QEMU's VIRTQUEUE_MAX_SIZE (1024) mapped-iov limit, the Linux virtio driver cannot carry more than ~4 MiB of inline command data, so legitimate submissions are unaffected. Fixes: 9d9e152136bd ("virtio-gpu: add 3d mode and virgl rendering support.") Fixes: 1dcc6adbc168 ("gfxstream + rutabaga: add initial support for gfxstre= am") Fixes: d52c454aadc ("contrib: add vhost-user-gpu") Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3776 Reported-by: admin@fluentlogic.org Signed-off-by: Marc-Andr=C3=A9 Lureau Reviewed-by: Akihiko Odaki --- contrib/vhost-user-gpu/vugpu.h | 8 ++++++++ include/hw/virtio/virtio-gpu.h | 8 ++++++++ contrib/vhost-user-gpu/virgl.c | 7 +++++++ hw/display/virtio-gpu-rutabaga.c | 8 ++++++++ hw/display/virtio-gpu-virgl.c | 8 ++++++++ 5 files changed, 39 insertions(+) diff --git a/contrib/vhost-user-gpu/vugpu.h b/contrib/vhost-user-gpu/vugpu.h index 654c392fbbf..0421c536403 100644 --- a/contrib/vhost-user-gpu/vugpu.h +++ b/contrib/vhost-user-gpu/vugpu.h @@ -163,6 +163,14 @@ struct virtio_gpu_ctrl_command { QTAILQ_ENTRY(virtio_gpu_ctrl_command) next; }; =20 +/* + * With 4 KiB pages and QEMU's VIRTQUEUE_MAX_SIZE (1024) mapped-iov + * limit, the largest inline command is ~4 MiB. Cap submit_3d + * allocations to this value to prevent a malicious guest from + * triggering an OOM abort via an inflated cs.size field. + */ +#define VIRTIO_GPU_MAX_CMD_SUBMIT_SIZE (4 * 1024 * 1024) + #define VUGPU_FILL_CMD(out) do { \ size_t vugpufillcmd_s_ =3D \ iov_to_buf(cmd->elem.out_sg, cmd->elem.out_num, 0, \ diff --git a/include/hw/virtio/virtio-gpu.h b/include/hw/virtio/virtio-gpu.h index f69fc194627..c10bfbd596f 100644 --- a/include/hw/virtio/virtio-gpu.h +++ b/include/hw/virtio/virtio-gpu.h @@ -299,6 +299,14 @@ struct VirtIOGPURutabaga { struct rutabaga *rutabaga; }; =20 +/* + * With 4 KiB pages and QEMU's VIRTQUEUE_MAX_SIZE (1024) mapped-iov + * limit, the largest inline command is ~4 MiB. Cap submit_3d + * allocations to this value to prevent a malicious guest from + * triggering an OOM abort via an inflated cs.size field. + */ +#define VIRTIO_GPU_MAX_CMD_SUBMIT_SIZE (4 * 1024 * 1024) + #define VIRTIO_GPU_FILL_CMD(out) do { \ size_t virtiogpufillcmd_s_ =3D \ iov_to_buf(cmd->elem.out_sg, cmd->elem.out_num, 0, \ diff --git a/contrib/vhost-user-gpu/virgl.c b/contrib/vhost-user-gpu/virgl.c index 51da0e3667f..550fd03bf5c 100644 --- a/contrib/vhost-user-gpu/virgl.c +++ b/contrib/vhost-user-gpu/virgl.c @@ -202,6 +202,13 @@ virgl_cmd_submit_3d(VuGpu *g, =20 VUGPU_FILL_CMD(cs); =20 + if (cs.size > VIRTIO_GPU_MAX_CMD_SUBMIT_SIZE) { + g_critical("%s: command buffer too large (%u)", + __func__, cs.size); + cmd->error =3D VIRTIO_GPU_RESP_ERR_INVALID_PARAMETER; + return; + } + buf =3D g_malloc(cs.size); s =3D iov_to_buf(cmd->elem.out_sg, cmd->elem.out_num, sizeof(cs), buf, cs.size); diff --git a/hw/display/virtio-gpu-rutabaga.c b/hw/display/virtio-gpu-rutab= aga.c index 6ff12639012..4d7d7b24592 100644 --- a/hw/display/virtio-gpu-rutabaga.c +++ b/hw/display/virtio-gpu-rutabaga.c @@ -351,6 +351,14 @@ rutabaga_cmd_submit_3d(VirtIOGPU *g, VIRTIO_GPU_FILL_CMD(cs); trace_virtio_gpu_cmd_ctx_submit(cs.hdr.ctx_id, cs.size); =20 + if (cs.size > VIRTIO_GPU_MAX_CMD_SUBMIT_SIZE) { + qemu_log_mask(LOG_GUEST_ERROR, + "%s: command buffer too large (%u)\n", + __func__, cs.size); + cmd->error =3D VIRTIO_GPU_RESP_ERR_INVALID_PARAMETER; + return; + } + buf =3D g_new0(uint8_t, cs.size); s =3D iov_to_buf(cmd->elem.out_sg, cmd->elem.out_num, sizeof(cs), buf, cs.size); diff --git a/hw/display/virtio-gpu-virgl.c b/hw/display/virtio-gpu-virgl.c index 60c78af06a4..d9e5b011049 100644 --- a/hw/display/virtio-gpu-virgl.c +++ b/hw/display/virtio-gpu-virgl.c @@ -607,6 +607,14 @@ static void virgl_cmd_submit_3d(VirtIOGPU *g, VIRTIO_GPU_FILL_CMD(cs); trace_virtio_gpu_cmd_ctx_submit(cs.hdr.ctx_id, cs.size); =20 + if (cs.size > VIRTIO_GPU_MAX_CMD_SUBMIT_SIZE) { + qemu_log_mask(LOG_GUEST_ERROR, + "%s: command buffer too large (%u)\n", + __func__, cs.size); + cmd->error =3D VIRTIO_GPU_RESP_ERR_INVALID_PARAMETER; + return; + } + buf =3D g_malloc(cs.size); s =3D iov_to_buf(cmd->elem.out_sg, cmd->elem.out_num, sizeof(cs), buf, cs.size); --=20 2.55.0